The first Chinese astronaut to be sent to space claims that he constantly heard a mysterious knocking sound that could potentially be created by aliens. (Photo : China Photos/Getty Images)

The Chinese space agency is ready to take on the international stage when it comes to space explorations but is China ready to meet alien life? Some Chinese astronauts said they've heard mysterious knocking sounds in space.

Another wave of speculations about alien life surfaced just when a Chinese astronaut claimed that he heard mysterious knocking and banging sounds in space during his flight in 2003. Yang Liwei is the first Chinese astronaut to reach space and he recounts that his first flight to space was clouded with mystery.

In a recent interview, Yang Liwei said the sound is similar to a hammer hitting a metal surface. During his mission to space, the astronaut claims that the sound appears and disappears constantly throughout the mission.

"A non-causal situation I have met in space is a knock that appeared from time to time," Yang Liwei said in a TV guesting in China according to IB Times. "It neither came from outside nor inside the spaceship but sounded like someone is knocking the body of the spaceship just as knocking an iron bucket with a wooden hammer," Yang Liwei added.

His claim was alleged supported by another unnamed Chinese astronaut who was with him during the mission. The now senior general and former astronaut also allegedly tried to inspect the source of the mysterious knocking sound to no avail. The sounds disappeared when Liwei returned to Earth, according to Daily Star.

And in a surprising twist, astronauts who reached space after Yang Liwei, also claim to have heard the sound during their mission aboard the Shenzhou 6 and Shenzhou 7. But Liwei already warned his colleagues about the mysterious sound. "Before entering space, I have told them that the sound is a normal phenomenon, so there is no need to worry," said Liwei in the same report.

Because of the bizarre nature of the sound, some suggest that it could be a sound of an alien, according to Express. But in a non-believer's point of view, it could be a part of the spacecraft constantly hitting each other but no one can tell for sure until the origin of the sound is identified.

But up to this day, the first Chinese astronaut is not expecting to find the source of the mysterious sound. He claims to have tried to recreate the banging sound but did not succeed.